1. Field of the Invention
The present invention relates to a fuel cell stack including a stack body formed by stacking a plurality of unit cells and a box-shaped casing containing the stack body. Each of the unit cells includes an electrolyte electrode assembly and separators sandwiching the electrolyte electrode assembly. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes.
2. Description of the Related Art
For example, a polymer electrolyte fuel cell employs an electrolyte membrane (electrolyte) comprising a polymer ion exchange membrane. The electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly. The membrane electrode assembly is sandwiched between separators to form a fuel cell.
In use, normally, a predetermined number (e.g., several tens to several hundreds) of fuel cells are stacked together as a fuel cell stack to achieve the desired power generation performance. In the fuel cell stack, in order to prevent the increase in the internal resistance of the fuel cells, and prevent degradation in the sealing performance for reactant gases, the fuel cells need to be held together reliably under pressure.
In this regard, for example, a fuel cell stack disclosed in Japanese Laid-Open Patent Publication No. 2002-298901 is known. The fuel cell stack has a stack body formed by connecting a predetermined number of unit cells electrically in series. Each of the unit cells includes an assembly including a cathode, an anode, and an electrolyte interposed between the cathode and the anode, and a pair of separators sandwiching the assembly. The separators have a fuel gas flow field for supplying a fuel gas to the anode, and an oxygen-containing gas flow field for supplying an oxygen-containing gas to the cathode. Current collecting electrodes are provided outside the stack body, and end plates are provided outside the current collecting electrodes. The stack body and the current collecting electrodes are placed in a casing having at least one detachable side surface. An opening at the end of the casing is connected to the end plate by a hinge mechanism.
In the hinge mechanism, a plurality of cylindrical insertion portions are provided in a mounting plate such as the end plate and the casing, and coupling pins are integrally inserted into the cylindrical insertion portions. Thus, a process of forming a plurality of cylindrical insertion portions integrally with the mounting plate is performed, and operation of fabricating the mounting plate is complicated. Further, it is necessary to achieve the desired fabrication accuracy. Consequently, the overall cost for producing the fuel cell stack is considerably high.